This invention relates to liquid ring pumps, and more particularly to liquid ring pumps with flow control vanes in the liquid ring of the pump.
Liquid ring pumps typically include an annular housing and a rotor rotatably mounted in the housing so that the rotor is eccentric to at least a portion of the housing. The rotor has a plurality of radially outwardly extending blades. A quantity of pumping liquid (e.g., water) is maintained in the housing so that when the rotor rotates, the rotor blades engage the liquid and form it into an annular ring around the inner periphery of the housing. Because of the eccentricity of the rotor relative to the housing, the amount of space between any two adjacent rotor blades which is occupied by ring liquid varies cyclically as the rotor rotates. The remaining space between adjacent rotor blades therefore forms pumping chambers which alternately expand and contract as the rotor rotates. The expanding pumping chambers are connected to a source of gas, vapor, or gas-vapor mixture (all of which are hereinafter referred to generically as gas) to be pumped, thereby drawing the gas into what is called the intake zone of the pump. The contracting pumping chambers are similarly connected to the desired sink of the pumped gas, thereby allowing the pump to discharge the pumped gas to that sink from what is called the compression zone of the pump.
In the portion or portions of the liquid ring in which the outer periphery of the rotor is relatively remote from the inner periphery of the housing (sometimes referred to herein as the sweep or sweeps of the pump), the immediate influence of the rotor on the liquid is relatively small. (As used herein and in the appended claims, the term "outer periphery of the rotor" or the like refers to the surface of revolution defined by the outer tips of the rotor blades as the rotor rotates about its axis). In the sweep of the pump the liquid must effect a turn which constitutes a substantial change in direction and must then begin to re-enter the rotor guided only by the inner periphery of the housing. In making this turn, considerable kinetic energy of the liquid may be lost due to such effects as the turbulent mixing of the low velocity liquid near the housing wall and the higher velocity liquid closer to the rotor. These energy losses are sometimes referred to for convenience herein as turning losses. The kinetic liquid energy lost in this way decreases the efficiency of the pump because the lost energy is not available either to perform the work of compressing the gas being pumped or for recovery as mechanical energy through momentum exchange with the rotor when the liquid re-enters the rotor.
Another source of inefficiency in pumps of the type described above is the fact that the velocity vector of the liquid re-entering the rotor typically is not optimal for efficient rotor re-entry. Depending on the angular location of re-entry, either the magnitude, or the direction, or both the magnitude and direction of the velocity vector of the re-entering liquid may differ substantially from the corresponding characteristics of the velocity vector of the liquid already entrained by the rotor. Substantial energy may be lost due to the shock associated with the nearly instantaneous acceleration or deceleration of the liquid re-entering the rotor as it is entrained by the rotor. These energy losses are sometimes referred to for convenience herein as shock losses.
In view of the foregoing, it is an object of this invention to provide improved liquid ring pumps.
It is another object of this invention to provide liquid ring pumps in which turning losses and/or shock losses are reduced to increase the efficiency of the pumps.
It is still another object of this invention to provide means for controlling the flow of pumping liquid in the sweeps of liquid ring pumps to improve and/or control the performance characteristics and/or efficiency of the pumps.